Optical glass



Nov. 21, 1961 w. GEFFCKEN ET AL 3,009,819

OPTICAL GLASS Filed Feb. 19, 1958 2 Sheets-Sheet 1 FIG. I

//VVN7'0RS:

WALTER 6'5 FHA F4 41/111011 FAl/Z may gu ly M Nov. 21, 1961 w. GEFFCKEN ET AL 3,009,819

OPTICAL GLASS Filed Feb. 19, 1958 2 Sheets-Sheet 2 S Q; 1- 81'0 5.0 Mal ATTO RA/E/S United States Patent 3,009,819 OPTIQAL GLASS Walter Geficken and Marga Faulstich, Mainz, Germany, assiguors to Jenaer Glaswerk Schott & Gem, Mainz, Germany, a corporation of Germany high content in expensive rare earths but they also contained considerable amounts of fluorine. Because of the high volatility of this substance, it was extremely dithcult to produce larger pieces of such glass which were free of any cords as required for optical purposes. l f 2 Z 7 it is therefore another object of the present invention Claims fif i g fgg f 195 to provide a glass of the type as above described which g may be melted Without any difficulties and will be free The P lnventlon felatfis a glass Wh 1ch has a of any cords. For attaining these objects, the glass ac- Y high Rim-95W index and 2 hlgh Abbe l0 cording to the present invention consists essentially of value 1!, and which is intended for optical purposes, and b i id d earth lk li Particularly for Optical Systems of the highest posslbls Although it has been known for some time that such power. systems have a glass range of a considerable extent, it A glass of this kind with a feffactlv? Index Pf was so far unknown and has now been found that Within h n 1. has already been produced p t0 thls mventhese ranges there are smaller zones in which the Abbe iiofi y the ifitmduciion of larger Components 9 z a value rises considerably above the maximum stated in and "1110 The highest possible Abbe value which could th abgve ti be attained in such a glass amounted" to about 58.5. The optical glass according to the present inVenti n Although Such a glass is quite valuable for o p consists of the system BaO, C210, and B 0 in a com- P were is Still 51 great new for a glass Wlth a Sun position ratio in moi-percent, the range of which within a high r Abbe value at a refractive n ex betweeu 1- triangular coordinate system is defined by a straight-lined and 1.64. The best possible glass of this kind which is connection between h values A B C D d E, as presently available in commerce has a refractive index of i di t d i FIG, 2, i whi h 1.6204 at an Abbe value of 60.2 and a content of A s B O :58, B'O=42, s1l1c1c acid of about 30%. It has also been found that B B L C 2 3 2 a a the refractlve lndex of such a glass can be varied be- C 1s B O 72, BaO 8, CaO 20, tween the values or 1.59 and 1.65, on the one hand, by 1 is D is .5 O -,2, uaO 23, CaO 5, and an addltion or bone acid and, on the other hand, by a p .4 1S B203-69, B3.031. replacement of BaO by means of 15 0 or T110 How- E l 1 ever, it has been further found that the Abbe value of It the optical glass accordmg to 1116 invention is defined such a glass when thus difi d does act as yet Comply 111 terms of weight-percent rather than in mol-percent, with the requirements of optical systems of the highest as Set forth: the followmg observed: power. A. B O =47.73, BaO=52.73

In the accompanying drawings, PEG. 1 shows a graph B. B O =59.49, BaO=12.41, Ca0=28.09 which illustrates that the best possible v-values of the 35 C. B O =71.84, BaO:12.08, CaO=16.08 known kinds of glass, although usually smaller, fall within D. B O =64.97, Ba0=31.40, Ca0=3.63, and a line X-Y. This line corresponds to the equation E. 3 0 :5994, BaO=40.46. v mH=6 WheI111 m means Specific examples of difierent kinds of glass of a comf POSSlble Abbe Vaiue attainable In a glass of position ratio according to the invention are indicated th s kind. below in Table 1 under section Ii, namely, from Ila to it is an ob cct of the present lnve lt on t0 p c a IIq, while the respective optical values of the different glass f r Opti al PIlFPOSBS Wlih Abbe Value greater kinds of glass are indicated in Table 2 under section II than 62.2(nd1.60).100 and disposed at the left of which also shows in the last column thereof the increase line X--Y in the graph accordmg to FIG. 1. in v over the values as indicated by the line X-Y in Alth ug glass of this W1 s a so been produced FIG. 1. Table 2 also shows that the Abbe values may prior to this invention the known kinds not only had a range as high as 3.4.

TABLE 1 Oxide Content of Basic Glass No. B203 020 BaO SrO molwt.- mol wt.- molwt.- molwt.- pcrcent percent percent percent percent percent percent percent 64. s 50. 05 10. 9 8.00 24. 3 32. 95 54.1 56. 16 4. 3 3. 03 31. 3 40. 81 51. 2 54. 07 s. 4 5. 9s 30. 4 39. 06 64. 2 01. 11 1s. 2 15. 95 17. 5 24. 93 65. 1 60. 77 14. 5 10. 20. 4 2s. 33 66. 3 66. 0s 23. 5 1s. 04 10. 1 14. 9s 71. 7 66. 12 8.1 0. 01 20. 3 27. so 74. 5 71. 84 12.8 9. 94 12. 7 s4. 2 54. 65 35.8 08. 5 50. 15 31. 7 67. 0 68. 19 5. 9 21. as 26. 1 54. 8 62. 7s 20. 4 15.91 14 8 s3. 6 54. 19 1s. 9 12. 97 17. 5 60.4 50.12 19.4 12. 95 20.2 59. 5 51. 12 23.1 15. 97 17.4 60.0 50. 00 21. a 14. 48 18.8 67. 7 57. 13 14. 7 9. 9s 17. 7 6s. 5 59.15 15. 8 10.99 15.7 59. 2 52.15 25. 3 17. 95 15. 4 60. 0 45. 25 11. 1 s. 74 2s. 9 53. 2 52.15 16. 5 10. 96 20. 3 59. 6 40. 12 40. 4 09. 0 50. 27 31.. 0 62.0 55.35 12.5 70.0 58. 74 17.9 54.5 45.21 35.5 59.8 43. 03 33.5 62.5 46. 05 30.8

TABLE 1.-Coritinu ed Oxide Content of Basic Glass B20; OaO BaO SiO: P105 F2111 No, place BeO, LizO, Laz'Og,

of 0, wt.- wt.- wt.= molwt.- molwt.- molwt.- molwt.- molwt.- wt.- perpererperperperperperperpcrpcrperperpercent cent c'ent cent cent cent cent cent cent cent cent cent cent cent A 59.9 51.15 14.5 9. 97 17.5 B 57.5 51.16 19.5 13.98 16.8 C- 58.5 50.87 21.7 15.20 17.2 In D"- 60.6 50.17 19.5 13.01 18.6 58.7 49.40 21.8 14.78 17.2 65.2 50.77 11.3 7.09 21.8 G- 59.4 50.42 22.05 15.08 17.4 H-" 61.6 19.9 1- 18.3

TABLE 2 compositions at any desired ratios with each other, and

11 Increase Other kinds of glass according to the invention consist of the system SrO, C110, and E in accmposition ratio in mol percent, the range of which within a triangular coordinate system is defined nas en -1mm connectlon between the values A, B, C, D, and E, as indicated in FIG. 3, wherein A is B O :60, SrO=40;

D is B O =76, SrO=15, 02.0 9; and E is B203:70,

The above optical glass compositions as defined in weight-percent are shown below:

Specific examples of difierentkinds of glass of this composition ratio according to FIG. 3 are indicated in Table 1 .under section I, while the respective optical values are again entered in Table 2 under section 1.

According to another feature of the invention, it is also possible .to mix the diflicrent .lc'inds of glass of the, above it has been found that in such a case the optical values will extensively add to each other.

It has been further found that it is possible to increase the chemical stability of the difierent kinds of glass according to the invention without affecting hteir optical values by replacing an amount in boric acid of up to 10 mol percent by means of SiO or P 0 Different examples of such kinds of glass are indicated in the triangular coordinate system as shown in FIG. 4 and in Table 1 in section III, while the respective optical values are indicated in Table 2 in section III.

The oxygen contained in the glass according to the invention may be replaced by fluorine at a maximum extent of 2 percent by weight without any noticeable effect due to the volatility ofthefluorine. Such replacement results in an increase in the Abbe value, which may also be attained by an addition of up to 1.5% by weight in M 0 to the glass compositions according to the invention. A similar effect may be attained by an addition of up to 3% in BeO.

It is also regarded as being within the scope of the present invention to add a total amount of up to 5% by weight in La O ZnO, and Q10, as well as up to 3% of other substances which are conventional in glass compositions, such as, for example, Al O Ta O or ZrO Like any other glass with a high content in boric acid, the new kinds of glass according to the invention also have an anomalous particle dispersion through which the blue end of the spectrum appears to be shortened.

Since the molten glass according to the invention is very thinly liquid and highly aggressive upon ceramic materials, the melting operation is preferably carried out in a platinum crucible. For refining the glass, temperatures of no moi'e than 1400 C. are required. The processes of casting the molten glass and of subsequently cooling it may be carried out in the conventional manner.

Although our invention has been illustrated and described with reference to the preferred embodiments thereof, .we .wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the apppended claims.

Having thus fully disclosed our invention, what we claim is:

1. An optical g lass composition having a refractory index of from 1.59 to 1.65 and an Abbe value v of 62.2(nd-1. 60).100, consisting of the system 1330, Ca() and B 0 in a composition ratio in weight-percent, the range of which within a triangular coordinate system is defined by a straight-lined connection between the values A, B, C, D and E, wherein A is B O =47.73, BaO=52.73

B is 3 0 :5949, 3210:1241, CaO=28.09

C is B O =71.84, Ba0=l2.08, OaO=16.08

D is B O =64.97, BaO=3l.40, CaO=3.63, and E is 3 0 :5954, BaO=40.4-6.

2. An optical glass having a refractory index of from 1.59 to 1.65 and an Abbe value v of consisting of the system SrO, CaO and E in a composition ratio in weight-percent, the range of which within a triangular coordinate system is defined by a straightlined connection between the values A, B, C, D and E, wherein A is B O =50.2O, SrO=49.8O

B is B O =61.O0, SrO=l3.62, CaO=25.38

C is 3 0 :7490, S1'O=13.20, CaO=11.90

D is B O =71.74, SrO=21.42, CaO=6.80, and E is B O =60.65, SIO=39.35.

3. Optical glass as defined in claim 1, wherein up to a total amount of weight-percent in boric acid is replaced by at least one member selected from the group consisting of 311d P205.

4. An optical glass composition having a refractory index 11d of from 1.59 to 1.65 and an Abbe value v of 62.2 (ndl.60).100, consisting of a mixture of glasses coming within the system BaO, C210 and B 0 in a composition ratio in weight-percent, the range of which Within a triangular coordinate is defined by a straightlined connection between the values A, B, C, D and E, wherein A is B2O3=47.73, 3210:5213

a is B2O3=59.49, BaO=12.41, CaO=28.09

c is 3,0,:71134, BaO=12.08, Ca0=16.08

D is B2O3=64.97, 3210:3140, Ca0=3.63, and n is 3 0 :5954, BaO=40.46.

5. An optical glass composition having a refractory index mi of from 1.59 to 1.65 and an Abbe value v of 62.2 (nd 1.60).100, consisting of a mixture of glasses coming within the system SrO, C210 and B 0 in a composition ratio in weight-percent, the range of which within a triangular coordinate system is defined by a straight- 0 lined connection between the values A, B, C, D and E, wherein B is 3 0 :6100, SrO=13.62, CaO=25.38

D is B O =7l.74, SrO=21.42, CaO=6.80, and E is B O =6O.65, SrO=39.35.

8. Optical glass as defined in claim 1, having an addition of up to 1.5% by weight in U 0.

9. Optical glass as defined in claim 1, having an addition of up to 3% by Weight in BeO.

10. Optical glass as defined in claim 2, having an addition of up to 1.5% by weight in Li O.

11. Optical glass as defined in claim 2 having an addition of up to 3% by weight in BeO.

References Cited in the file of this patent UNITED STATES PATENTS 1,570,876 Compton Jan. 26, 1926 2,090,098 Berger et al Aug. 17, 1937 2,294,844 Gelstharp Sept. 1, 1942 2,434,146 De Paolis Jan. 6, 1948 2,466,392 De Paolis Apr. 5, 1949 2,517,459 Armistead Aug. 1, 1950 2,584,974 Armistead Feb. 12, 1952 2,764,492 Weissenberg et a1 Sept. 25, 1956 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 3,00%819 November 21 1961 Walter Geffcken et al,

In the drawings sheet 2 thereof lower left corner name of inventor, for "WALTER GEFFKEN" read WALTER GEFFCKEN column 8, in TABLE 2 column 3 thereof line 7 for "6286" read 63n6 column l line 23, for "hteir" read their Signed and sealed this 17th day of April 1962,

(SEAL) Attest:

ESTON Go JOHNSON DAVID L LADD Attesting Officer Commissioner of Patents 

1. AN OPTICAL GLASS COMPOSITION HAVING A REFRACTORY INDEX OF FROM 1.59 TO 1.65 AND AN ABBE VALUE V OF >62.2-(ND-1.60).100, CONSISTING OF THE SYSTEM BAO, CAO AND B2O3 IN A COMPOSITION RATIO IN WEIGHT-PERCENT, THE RANGE OF WHICH WITHIN A TRIANGULAR COORDINATE SYSTEM IS DEFINED BY A STRAIGHT-LINED CONNECTION BETWEEN THE VALUES A, B, C, D AND E, WHEREIN 